GB2152025A

GB2152025A - Basic refractory compositions

Info

Publication number: GB2152025A
Application number: GB08432731A
Authority: GB
Inventors: Naresh Bikash Dasgupta; Gunter Gelsdorf; Thomas Weichert
Original assignee: Didier Werke AG
Current assignee: Didier Werke AG
Priority date: 1983-12-28
Filing date: 1984-12-28
Publication date: 1985-07-31
Also published as: IT1178441B; AT382144B; GB2152025B; DE3347250A1; GB8432731D0; IT8449235A0; DE3347250C2; FR2557564B1; FR2557564A1; ATA396484A

Abstract

A basic refractory brick or composition based on a mixture of olivine and magnesia, or on magnesium aluminium spine, contains celsian (or components capable of forming celsian) when fired in an amount of 1 to 20 weight-%, calculated as barium oxide. The composition may be used for lining a rotary tubular cement furnace or the regenerator of a glass tank furnace.

Description

SPECIFICATION Basic refractory bricks or compositions The present invention relates to basic, refractory bricks or compositions based on mixtures of olivine and magnesia or based on magnesium aluminium spinel, especially for lining rotary tubular cement furnaces or the regenerators of glass tank furnaces, and relates also to a method of manufacture of such fired bricks and to the use of such basic, refractory bricks or compositions.

Ceramic compositions based on celsian, i.e. BaO-AI203-2Sio2, are disclosed in German Patent 536 799. Moulded bodies manufactured from these ceramic compositions have an improved resitance to bases. These compositions, however, contain predominantly the components necessary to form celsian when they are fired and no other refractory materials.

It is an object of the present invention to provide basic, refractory bricks or compositions which have an improved strength and improved corrosion re sistance to alkali salts from the raw cement powder and to alkali and S03 containing furnace gases compared to fired or chemically bonded basic bricks based on mixtures of olivine and magnesia or on magnesium aluminium spinel, the bricks or compositions according to the invention achieving their advantageous properties after being fired at lower than usual temperatures or used at lower than usual temperatures.

According to the present invention there is provided a basic, refractory brick or composition based on a mixture of olivine and magnesia or on rnagne- sium aluminium spinel which contains celsian or components capable of forming celsian when fired in an amount of 1 to 20 weight-%, preferably 3 to 8 weight- /O, calculated as barium oxide.

The invention relates also to a method of manufacturing a basic refractory brick including forming a composition based on a mixture of olivine and magnesia or on magnesium aluminium spinel and containing celsian or components capable of forming celsian when fired in an amount of 1 to 20 and preferably 3 to 8 weight-% and then firing the composition whereby celsian is present or formed in the resulting brick. The composition may be fired at 1100 to 1 500 C and in the preferred form of the method barium sulphate is added to the composition as a component necessary for and capable of forming celsian.

The manufacture of the basic, refractory bricks or compositions is effected in any conventional manner by mixing the starting materials in suitable grain sizes.

Olivine is a naturally occurring material which may be readily recovered and then reduced to the desired grain size. The olivine material can be used with a grain size of 0 to 6 mm, preferably 0 to 3 mm. The magnesia is advantageously used in the form of sintered magnesia with a conventional grain size, advantageously with a grain sixe of 0 to 0.2 mm. Magnesium aluminium spinel (MgO-AI203) is preferably used as a presintered material, also with the conventional grain size distribution, e.g. 0 to 6 mm, advantageously 0 to 3 mm. The magnesia in the olivine magnesia mixture is preferably present in an amount of 2 to I0weight-%.

If the brick or composition is based on an olivine magnesia mixture, magnesium aluminium spinel can be present also in the original mixture, e.g. in an amount of 5 to 15 weight-%.

The celsian in the bricks or compositions accord- ing to the invention is preferably in powdered form, i.e. having a grain size of 0 to 6 mm. If the celsian is not added as a preformed product, but in the form of the components capable of forming celsian when fired or used at a firing temperature, either barium carbonate, or preferably barium sulphate, in finely powdered form, i.e. as a powder having a grain size less than 0.09 mm and preferably 0.04 mm can be used to yield barium oxide.Finely divided Awl203 and!or SiO2 containing materials such as corundum, calcined alumina, refractory clay, aluminosilicates (approximate composition Al203-SiO2, e.g. andalusite, cerphalite), quartz, vitreous silica and pyrogenic silica may be added as a further component for forming celsian at firing temperatures. These Awl203/ SiO2 yielding components are preferably also used in finely powdered form, i.e. with a grain size less than 0.09 mm and preferably less than 0.04 mm.

The quantitative relationship of the components capable of forming celsian is so chosen that the formation of the celsian phase, i.e. BaO-AI203-2SiO2 is possible. Small excess amounts or deficiencies of Awl203 or SiO2 do not matter since apart from the celsian other mineral phases and/or glass phases are formed in smaller amounts.

Further additives usually used in the refractory field can be used in the manufacture of the basic, refractory bricks or compositions. Examples of these are organic bonding agents, i.e. temporary bonding agents such as sulphite water or bonding agents inducing a chemical bond such as magnesium sulphate or sodium polyphosphate. Water may also be used in the manufacture of the bricks or compositions as necessary, the amount of water depending on the type of product being manufactured. The amount of water can, however, be simply determined with the help of preliminary tests.

Further features and details of the invention will be apparent from the following Examples: Example 1 5 parts by weight of magnesia having a grain size of 0 to 0.2 mm, 45 parts by weight of olivine having a grain size of 1 to 6 mm and 50 parts by weight of olivine having a grain size of 0 to 1 mm were throughly mixed in a mixer. 10 parts by weight of barium sulphate powder having a grain size less than 0.09 mm and 15 parts by weight of cerphalite having a grain size less than 0.09 mm were added thereto. Additionally 2.4 parts by weight sulphite waste as a temporary, organic bonding agent and 1 part by weight water were added to the mixture and thoroughly mixed in. Bricks were formed from this mixture and were fired at 1 450 C in a tunnel kiln after having been dried at 120 C.

Example 2 The method of Example 1 was repeated, but using 5 parts by weight magnesia, 10 parts by weight magnesium aluminium spinel and 40 parts by weight olivine having a grain size of 1 to 6 mm and 45 parts by weight olivine having a grain size of 0 to 1 mm.

Bricks having a gross density of 2.71 and a cold resistance to compression of 90 N/mm2 were obtained.

Example 3 A synthetically produced magnesium aluminium spinet was used as the refractory starting material in this Example. The grain size distribution of the spinel was as follows: 30 weight % 0 to 0.1 mm 50 weight % 0.1 to 2 mm 30 weight % 2 to 4 mm.

The method of Example 1 was repeated, i.e. for each 100 parts byweight magnesium aluminium spinel 10 parts by weight barium sulphate powder and 15 parts by weight cerphalite powder were added.

The bricks manufactured from this mixture were also fired in a tunnel kiln at 1450 C.

Claims

CLAiMS

1. A basic, refractory brick or composition based on a mixture of olivine and magnesia or on magnesium aluminium spinel which contains celsian (BaO-AI203-2SiO2) or components capable offorming celsian when fired in an amount of 1 to 2Q weight-%, calculated as barium oxide.

2. A brick or composition as claimed in claim 1, which contains celsian or components capable of forming celsian when fired in an amount of 3 to 8 weight-%, calculated as barium oxide.

3. A brick or composition as claimed in claim 1 or claim 2 based on a mixture of olivine and magnesia which also includes a proportion of magnesium aluminium spinel.

4. A brick or composition as claimed in claim 1 which has been fired at 1100 to 1 500 C.

5. A basic refractory brick or composition substantially as specifically herein described with reference to any of the accompanying Examples.

6. A method of manufacturing a basic refractory brick including forming a composition based on a mixture of olivine and magnesia or on magnesium aluminium spinel and containing celsian or components capable of forming celsian when fired in an amount of 1 to 2û weight-% and then firing the composition whereby celsian is present or formed in the resulting brick.

7. A method as inclaim8inwhichthe composition is fired at 1100 to 1 500 C.

8. A method as claimed in claim 6 or claim 7 in which barium sulphate is added to the composition.

9. A basic, refractory brick or composition as claimed in any one of claims 1 to 5 in use in lining a rotary tubular cement furnace or the reg enerator of a glass tank furnace.